The Bosch Extra Hard Screwdriver Phillips Bit is a good choice for universal use. Made using S2 Modified Steel and an optimised heat treatment process for an 'extra-hard' quality for an adequate performance. The tapered torsion zone copes easily with torque peaks, fulfilling all tasks. The hex shank provides a strong connection and maximum torque transmission in three-jaw chucks and 1/4in internal hex tool holders. Suitable for use with rotary drills/drivers.